FRACTURE PATTERN AND STRESS ANALYSIS BASED ON BOREHOLE IMAGES AND SEISMIC ATTRIBUTES

Since fracture behaviour tends to be localized, integration of borehole image and
seismic attributes is believed to decrease the uncertainty in characterizing high
fracture density areas. The project objective is to delineate the fracture pattern
trends using borehole images and seismic attributes in the fractured basement of
the Anding field. The metasediments of Tanjung Kempit is chosen as the onshore
analogue as certain researchers believe them to represent uplifted basement rocks
of Peninsular Malaysia. In the onshore analogue, azimuth and dip of the major
highly dipping conjugate fractures and minor gently dipping tensile fractures
were measured and analysed. It is believed that the area underwent two phases of
an E-W compressional and a transpressional event which folded the formation
forming the conjugate and tensile fractures. Seismic interpretation of faults and
top of basement structure was done. Interpretation of fractures and foliation in
FMI data of Well X and Well Y was done and the high fracture density areas
were correlated with the ant tracking cube and amplitude cube generated from the
seismic. Fractures were extracted from the ant track cube and their azimuth and
dips were compared with the FMI interpretation and onshore analogue. The
highly dipping fractures (>50°) in the seismic are fault associated fractures as
they have major WNW-ESE azimuth similar to the interpreted faults. The gently
dipping fractures (<50°) are sheet fractures as they also have NW-SE orientation
similar to the foliation/bedding measured from FMI and also the bedding of the
onshore analogue. The onshore analogue fractures couldn’t be correlated well
with the offshore data due to differences in age, lithology and less focus on fault
associated fractures.